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Radio Telescope Proves A Big Bang Prediction

After 271 20-hour nights of staring at the Antarctic sky, a radio telescope at the South Pole has confirmed a critical prediction of the Big Bang theory of the origin of the universe, astronomers from the University of Chicago and the University of California announced here today.

The result reassured cosmologists that their theories of the universe were on track and pioneered a new technique that greatly increases cosmologists' ability to know what was going on in the early universe.

Using their telescope in effect as a pair of Polaroid sunglasses, the team, headed by Dr. John Carlstrom of Chicago, discovered that a faint radio haze thought to be the fading remnant of the Big Bang itself is slightly polarized. That is to say, its flickering electromagnetic fields that constitute light waves were not completely jumbled, vibrating in all different planes as they sped to Earth, like feathers sticking out at all angles at the end of an arrow. Rather, they showed a slight preference for one plane of vibration, as if all the feathers lined up.

That, theorists say, is the predicted signature of the last bounce of light from hot, electrified cosmic gases just as the universe was cooling to the point where atoms could form, 400,000 years after the universe was born.

''The prediction is bang on,'' Dr. Carlstrom told a rapt audience of more than 200 cosmologists at a conference at the Adler Planetarium here. ''We think we know the universe, but if the polarization is not there at the predicted level we're back to the drawing board.''

The findings lend more credence to many of the more preposterous-sounding conclusions that have made headlines over the last few years, which have united famously fractious cosmologists in a view of a universe born 14 billion years ago -- a view in which ordinary matter is swamped with mysterious dark matter and dark energy and is apparently accelerating into the cosmic night.

''We're stuck with a preposterous universe,'' Dr. Carlstrom said. Two papers describing the work will be posted on the team's Web site, astro.uchicago.edu/dasi, he said.

Other cosmologists responded with a mixture of glee and relief, saying it would have been bigger news if the polarization had not been found. ''If you had any doubts that this radiation is from the Big Bang, this should quash them,'' said Dr. Michael Turner, a cosmologist at the University of Chicago.

Dr. Martin Rees, a cosmologist at the University of Cambridge and the Astronomer Royal, who suggested looking for polarization in the cosmic radiation 34 years ago, said it was ''gratifying'' but emphasized that it was only the first step in a campaign to understand the early universe.

Dr. Max Tegmark, a cosmologist at the University of Pennsylvania, said, ''In my opinion, this is huge and marks the beginning of a a new era in cosmic microwave background research.''

The observations also represented another notch in the belt for one of the most controversial ingredients in the standard model of the Big Bang. Known as inflation, it posits that the universe underwent a hyperexplosive growth spurt early in its existence. Although it is successful as a theory, astronomers admit that they do not know what caused inflation or precisely when it happened.

The new results are consistent with inflation but do not establish it as unquestionable truth. Future polarization measurements, with more sensitive radio telescopes, Dr. Carlstrom said, might detect the roiling of space left behind by its wrenching outburst and confirm that it had happened and when. ''We can go from checking inflation to actually testing it,'' Dr. Carlstrom said.

The cosmic radiation has transfixed astronomers since it was discovered in 1965 by two Bell Laboratories radio astronomers, Dr. Arno Penzias and Dr. Robert Wilson; they later received the Nobel prize. According to theoretical calculations, this radiation is in effect a snapshot of the universe at an age of 400,000 years. But water vapor in the atmosphere and the faintness of the microwaves makes them hard to study except from satellites or balloons or very high altitude observatories. The South Pole instrument, known as DASI, for Degree Angular Scale Interferometer, is about two miles high, Dr. Carlstrom said, and since it is so cold in Antarctica, the air holds very little water vapor.

Since 1992 NASA's COBE satellite and a host of smaller instruments have examined the cosmic background and confirmed that faint ripples or blotches -- the seeds of future cosmic structures like galaxies -- follow the pattern predicted by inflationary models. But while mapping these blotches reveals the distribution of matter at that time in the universe, Dr. Carlstrom said, mapping the polarization of the cloud tells how the material is actually moving and has the potential of containing much more information. ''It's like going from a black-and-white television to color,'' he said.

For the last year, polarization measurements have been the Next Big Thing in cosmology, with telescopes like DASI being converted to that purpose. Dr. Carlstrom's group won the race today, but the bigger race is only beginning, the cosmologists say. At least a tenfold increase in sensitivity is needed to detect the signature of inflation in the cosmic background, so-called gravitational waves that would ripple space itself, according to Einstein's general theory of relativity. Dr. Turner has called these the ''smoking gun'' signature of inflation. Most experts agree that a new generation of satellites and telescopes will be needed to pull it off, but they seemed invigorated by the challenge today.

''It's so exciting to see if we could test inflation,'' Dr. Carlstrom said, ''to be able to look at the universe at 10 (-30) seconds.''